# What is "electron affinity"?

$M \left(g\right) + {e}^{-} \rightarrow {M}^{-} \left(g\right) + \Delta$
Disbarring the Noble Gases, electron affinities generally INCREASE across a Period from left to right as we face the Table, and DECREASE down a Group.....and this is a function of nuclear charge, i.e. $Z$, $\text{the atomic number.}$